Cams are rotating or reciprocating elements that impart motion to followers. There are various types of cams including wedge, flat, radial, offset, cylindrical, spiral, conjugate, and globoidal cams. Followers can be classified based on their surface contact with the cam, type of motion, and line of motion. Key aspects of cam design include the base circle, prime circle, pitch point, pitch circle, trace point, pitch curve, cam angle, lift, cam profile, and pressure angle. Proper cam design considers factors like wear reduction, side thrust minimization, and optimal follower motion.

1. CAMS & FOLLOWERS
Cam
Follower
Followers
(valves)
Cams
A cam is rotating or a reciprocating element of a
mechanism , which imparts rotating, reciprocating
or oscillating motion to another element, called
follower. There is line contact between the cam
and the follower, and thereby forms a higher pair.

2. Classification of Cams
1. Wedge and flat cams: Such a
cams has wedge “A” to
which translational motion
is given to actuate the
follower “B” in order to
either reciprocate or
oscillate it in fig 1(a) & 1(b).
The follower is guided in
guides “C”. In fig 1(C), the
cam is stationary and the
follower guide C cause the
relative motion of cam A
and follower B. Fig 1(d)
shows a flat plate with a
groove in which the
follower is held to obtain
desire motion.

3. 2. Radial and offset cams: A cam in
which the follower moves
radially from centre of
rotation of the cam is called
a radial (or disc or plate)
cam, as shown in fig 2(a) and
2(b). The axis of follower
passes through the axis of
the cam. If axis of the
follower does not pass
through the axis of cam, it
is called an offset cam, as
shown in fig 2(C).

4. 3. Cylindrical cams: In a cylindrical
cam, a cylinder which has a
circumferential groove cut in
the surface, rotates about its
axis. The follower motion can
be either oscillatory or
reciprocating type, as shown
in fig 8.3 (a) and (b). They also
called barrel or drum cams.
4. Spiral CAMS: A spiral cam is a
face cam in which groove is
cut in form of spiral as shown
in fig 8.4. Spiral groove
consists of teeth which mesh
with pin gear follower.

5. 5. Conjugate cams: It is a double disc
cam in which the two discs keyed
together are in constant touch
with the two rollers of a follower,
as shown in fig 8.5. Such a cam
give low wear, low noise, better
control of follower, high speed,
high dynamic load.
6. Globoidal cams:
A globoidal cam has either a
convex and a concave surface. A
circumferential groove cut on
surface of rotation of cam to
impart motion to follower, which
has oscillatory motion as shown in
fig 8.6. This is used where angle of
oscillation is large.
7. Spherical cams: The spherical cam is
in form of spherical surface in
which follower oscillates about an
axis perpendicular to the axis of
rotation of the cam.

6. Types of Followers
1. According to surface in contact
Followers are classified by the surface contact between cam and
follower is generally come in this group. There are different type
of surface contact between cam and follower and according
surface contact they are classified as follows:
(a) Knife edge follower
As per name knife follower has knife
edge and knife edge has a surface
contact with cam profile (cam profile is
a shape of cam). As follower has knife
edge, so that there is more wear
between follower and cam profile. Due
to wear cam profile change with time
and does not work correctly. That is
reason due to which knife edge is not
use in practice.

7. (b) Roller follower
As per name roller follower has roller and surface contact
between cam and follower is rolling contact. It reduces wear of
cam profile.
(c) Spherical follower
In flat face follower, stresses are produce. In order to reduce this
stresses flat face is machined into spherical shape called as
spherical follower.

8. 2. According to type of follower motion
In this category followers are classified by the relative motion
and movement between cam and follower these are as follow.
(a) Translatory motion type follower
In this type of follower, follower have translatory motion means
cam is rotating and follower reciprocating between guide way.
Example of this type follower is knife edge follower, roller
follower, flat follower and spherical follower.
In this type of follower,
follower has oscillating
motion. Cam rotates and as per
cam profile follower also
move but follower is fixed at
point about which follower is
oscillate. This type of follower
is called as oscillatory motion
follower.
(b) Oscillatory motion type follower

9. (3) According to line of follower motion
(a) Radial follower:
In radial follower, axis of follower and centre of cam are in one
line or axis of follower is passing through centre of cam is called
as radial follower. Example of this type follower is knife edge
follower, roller follower, flat follower and spherical follower
(b) Offset follower
In offset follower, axis of follower movement is offset
from the centre of cam about which cam rotate is known as
offset follower.

10. Cam Nomenclature
1. Base Circle: The smallest circle drawn, tangential to the cam profile, with its
center on the axis of the camshaft. The size of the base circle determines the
size of the cam.
2. Prime Circle: The smallest circle drawn, tangential to the pitch curve, with
its center on the axis of the camshaft.
3.Pitch Point: Pitch point corresponds to the point of maximum pressure
angle, and a circle drawn with its centre at the cam centre, to pass through the
pitch point, is known as the pitch circle.
4. Pitch Circle: It is the circle drawn through the centre and pitch point.
5.Trace Point: It is a point on the follower, ands its motion describes the
movement of the follower.
6. Pitch Curve: It is the curve generated by the trace point as the follower
moves relative to the cam.
7. Cam Angle: It is angle turned through by the cam from initial position.
8. Lift: It is the maximum travel of the follower from the lowest position to the
topmost position. It is also called throw or stroke of the cam.
9. Cam Profile: The surface in contact with the follower is known as the cam
profile.

11. 10. Pressure Angle: The angle between the direction of the follower
movement and the normal to the pitch curve at any point is called pressure
angle. Pressure angle varies from maximum to minimum during complete
rotation. Higher the pressure angle higher is side thrust and higher the
chances of jamming the translating follower in its guide ways.
The pressure angle should be as small as possible within the limits of design.
The pressure angle should be less than 450 for low speed cam mechanisms
with oscillating followers, whereas it should not exceed 300 in case of cams
with translating followers. The pressure angle can be reduced by increasing
the cam size or by adjusting the offset.
11. Angle of Ascent: It is the angle of rotation of cam during which the
follower rises up.
12. Angle of Descent: It is the angle of rotation of cam during which the
follower lower down.
13. Angle of Dwell: It is the angle of rotation of cam during which the
follower remain stationary.

12. Cam Nomenclature